~anthropic/claude-sonnet-latest → B (6:4)

Both are substantial infra additions, but B fixes a real correctness/UX issue (fetch_entity returning immediately without waiting for the actual reddit fetch, replaced with a proper SSE stream with fetching/complete/error states and oneshot completion signaling), adds meaningful observability (tracing::debug throughout reddit worker), and updates the integration test to verify actual behavior end-to-end. A is a solid new feature (POST /ui plumbing and form templating) but is more scaffolding/wiring without fixing a functional gap, and B's SSE mechanism is the more durable, correctness-improving design.